Drawer slides have long been recognized as the best means by which durable, smooth-acting and quiet operation can be achieved. The drawer slide industry has increased in importance as a result of a corresponding increase in the demand for high quality residential and office furniture. The response by the drawer slide industry has been continuous improvement in the supporting technology of drawer slide design.
The usage of drawer slides in various applications has resulted in an industry specific designation of "precision" drawer slides which are generally viewed as those slides used in the more demanding applications. These particular uses include, among others, drawers in file cabinets (both vertical and lateral) and desk drawers, especially where the carrying weight expected to a pair of slides is in excess of 80 or 90 pounds. While the designation itself may not be "precise," the construction of the drawer slides in this category is precise. In order to meet the functional demands of the more demanding applications, it has been found that precision construction of the drawer slide is a necessity. Only by reducing tolerances of the many components that make up the final product can the appropriate "fit" and "feel" that is deemed acceptable in the industry be achieved.
Generally, drawer slide design in the precision category has evolved into the usage of ball bearings contained within telescoping channel members. This design has fairly met the challenge of achieving both the "fit" and "feel," as well as standing up to the desired weight loadings. The channel construction, as will be explained further within the present application, has typically been formed in such a way as to provide a raceway for the bearings to travel in. This contributes to the controlled transitioning of the slide in operation while retaining the ability to spread the loading on the ball bearings. While many variations on this theme are known in the art, the fundamental approach to the design of these ball bearing precision drawer slides has remained substantially as described.
The aforementioned ball bearing precision slide is not without its limitations. The failure mode of these slides has been studied with the result that the effects of exceeding the rated loadings are becoming known. This overload condition can occur in both a vertical and lateral manner and is quite often the sole cause behind slide failures. The industry has long suffered under the limitations of the prevailing drawer slide designs, even to the point where an ad hoc nomenclature has been applied to these products, identifying them by weight limitations, e.g., "75 pound class," "100 pound class," etc.
More specifically, classic failure of the lower arcuate track of a slide, particularly the outer axial end of the cabinet slide, is exhibited by the so-called "opening up" or "unrolling" of the lower arcuate ball track. This ball track, arcuate in cross section, exhibits a condition where the free lateral edge portion of the arc straightens out so as to be basically tangential to the arcuate curve. As a result, the slide does not retain the end ball bearings up in alignment with the other ball bearings. This allows the opening and/or open drawer to slope downwardly toward the outer end, and destroys effective, smooth operation of the slide. It is not uncommon for failure to occur even after only about 25,000-30,000 cycles.
The present invention relates to an improved unique channel design that has been found to correct the aforementioned failure condition.